Currently, to reduce air pollution due to vehicle exhaust gas, vehicles are being produced based on research conducted to ensure driving force using an internal combustion engine and/or an electric motor. As such, the vehicles have been evolved in the order of hybrid vehicles, plug-in hybrid vehicles, and electric vehicles. In this case, the hybrid vehicles and the plug-in hybrid vehicles include an internal combustion engine, an electric motor, and a battery pack, and the electric vehicles do not include an internal combustion engine but include an electric motor and a battery pack.
The battery pack has been evolved along with the hybrid vehicles, the plug-in hybrid vehicles, and the electric vehicles. The battery pack is configured to be rechargeable inside and outside an electric vehicle. The battery pack includes a battery module including battery cells, and an interconnect board (ICB) assembly (hereinafter referred to as an ‘electrode lead connecting structure’) electrically connected to the battery cells). The battery cells are sequentially and vertically stacked on one another in one direction. Each battery cell includes two electrode leads extending in one direction.
The electrode lead connecting structure is electrically connected to a battery management system (BMS), and includes a printed circuit board, a plurality of sensing busbars, and two electrode busbars. The printed circuit board is provided in a rectangular shape and includes an electrical circuit configured to measure voltages of the battery cells. Equal numbers of the sensing busbars are arranged at opposite edges of the printed circuit board. That is, pairs of the sensing busbars are alternately arranged at one side edge and an opposite side edge of the printed circuit board.
The sensing busbars are electrically connected to the printed circuit board to sense the voltages of the battery cells. The two electrode busbars are separately welded to a highest-potential sensing busbar, which receives the highest potential, and a lowest-potential sensing busbar, which receives the lowest potential, among the sensing busbars. The highest-potential sensing busbar corresponds to a bottom sensing busbar among the sensing busbars arranged at the one side edge of the printed circuit board, and the lowest-potential sensing busbar corresponds to a top sensing busbar among the sensing busbars arranged at the opposite side edge of the printed circuit board.
The electrode busbars receive power from the battery management system and supplies the power to the electrode lead connecting structure. In this case, the electrode lead connecting structure is located adjacent to the electrode leads of the battery cells and is configured to electrically interconnect the battery cells in series using the printed circuit board based on coupling among the sensing busbars, the two electrode busbars, and the electrode leads of the battery cells. The sensing busbars, the two electrode busbars, and the electrode leads of the battery cells are coupled to each other by welding one electrode lead to each electrode busbar and welding two electrode leads to each of the sensing busbars other than the highest-potential sensing busbar and the lowest-potential sensing busbar.
The electrode lead connecting structure senses the voltage of each battery cell using the printed circuit board and transmits an electrical signal about the sensed voltage to the battery management system. However, the electrode busbar is welded twice to be coupled to the highest-potential sensing busbar or the lowest-potential sensing busbar, and to be coupled to the electrode lead. The number of welding processes increases man-hours required to produce a battery pack. Furthermore, the probability that the welded part of the electrode busbar is separated from the sensing busbar and/or the electrode lead due to vibration of the vehicle or impact from a peripheral structure of the electrode lead connecting structure is very high.
Separation of the electrode busbar from the sensing busbar disables supply of power to the electrode busbar and deteriorates electrical characteristics of the electrode lead connecting structure, and separation of the electrode lead from the electrode busbar disables measurement of the voltage of the battery cell corresponding to the electrode busbar using the printed circuit board. In addition, since pairs of the sensing busbars are alternately arranged at the one side edge and the opposite side edge of the printed circuit board, at least one of the sensing busbars may not be bonded to the electrode lead of the battery cell due to a mistake.